Design optimization of bonded PM BLDC motors with reference to the cogging torque amplitude

With regard to small DC brushless motors the problem of the cogging torques amplitude is considered. At the aim a special motor prototype, obtained by the substitution of the original ferrite magnets with bonded magnets prepared in the own laboratories, has been realized; such a prototype assumes the role of "reference motor" as regards some quantities introduced as "quality factors" in the paper. One of the quality factors is concerning the cogging torques and has been evaluated for different hypothesis of the design modifications with respect to the reference motor. The analysis is performed through a simulation model which has been previously validated (for the case of the reference motor), by the comparison of the simulated results and the ones obtained from the experimental activity performed through a special test bench realized at the scope. The evaluation of the cogging torque amplitude for every hypothesis, allows to choose the optimal design modifications set for which the general motor performances are improved without a worsening of the cogging torque.